RESUMEN
Hazelnut (Corylus avellana), a nut crop that is rapidly expanding worldwide, is endangered by a rot. Nut rot results in hazelnut defects. A survey was conducted in north-western Italy during 2020 and 2021 to identify the causal agents of hazelnut rots. Typical symptoms of black rot, mold, and necrotic spots were observed on hazelnut nuts. The prevalent fungi isolated from symptomatic hazelnut kernels were Diaporthe spp. (38%), Botryosphaeria dothidea (26%), Diplodia seriata (14%), and other fungal genera with less frequent occurrences. Among 161 isolated Diaporthe spp., 40 were selected for further analysis. Based on morphological characterization and multi-locus phylogenetic analysis of the ITS, tef1- α, and tub2, seven Diaporthe species were identified as D. eres, D. foeniculina, D. novem, D. oncostoma, D. ravennica, D. rudis, and D. sojae. D. eres was the main species isolated from hazelnut rots, in particular from moldy nuts. Pathogenicity test performed on hazelnut nuts 'Tonda Gentile del Piemonte' using a mycelium plug showed that all the Diaporthe isolates were pathogenic on their original host. To our knowledge, this work is the first report of D. novem, D. oncostoma and D. ravennica on hazelnut nuts worldwide. Diaporthe foeniculina, D. rudis, and D. sojae were reported for the first time as agents of hazelnut nut rot in Italy. Future studies should focus on the comprehension of epidemiology and climatic conditions favoring the development of Diaporthe spp. on hazelnut. Prevention and control measures should target D. eres, representing the main causal agents responsible for defects and nut rot of hazelnuts in Italy.
RESUMEN
Gnomoniopsis castaneae is responsible for brown or chalky nut rot in sweet chestnut (Castanea sativa), causing heavy reductions in nut production. Controlling it is challenging, due to its inconspicuous infections, erratic colonization of host tissues and endophytic lifestyle. Fungicides are not applicable because they are prohibited in chestnut forests and strongly discouraged in fruit chestnut groves. Trichoderma species are safe and wide-spectrum biocontrol agents (BCAs), with a variety of beneficial effects in plant protection. This study tested selected strains of T. viride, T. harzianum and T. atroviride for their ability to suppress G. castaneae. Field experiments were conducted in four chestnut groves (two test plots plus two controls) at two sites with a different microclimate. As the size of the trees were a major drawback for uniform and effective treatments, the Trichoderma strains were delivered directly by trunk injection, using the BITE® (Blade for Infusion in TrEes) endotherapic tool. The BCA application, repeated twice in two subsequent years, significantly reduced nut rot incidence, with a more marked, presumably cumulative, effect in the second year. Our data showed the tested Trichoderma strains retain great potential for the biological control of G. castaneae in chestnut groves. The exploitation of Trichoderma spp. as biopesticides is a novelty in the forestry sector and proves the benefits of these microbes in plant disease protection.